Storage control apparatus and control method for virtual logical volume

Abstract

A controller 2 uses a virtual logical volume 3 having an expandable volume size to perform either a remote copy or an internal copy without suspending access from a host. The virtual logical volume 3 is able to expand a volume size in units of a cylinder group 6 that have a size equivalent to 25 pages. Information for managing a copy is stored in a control area 6 B inside the cylinder group 6. This enables storing of copy management information in accordance with the expanded size of the virtual logical volume.

1 . A storage control apparatus, comprising:
 a virtual logical volume, which is a virtually created logical volume and which is accessed from a host computer;   a pool which has a real storage area that is allocated to the virtual logical volume; and   a controller, which controls the allocation of the real storage area to the virtual logical volume, and which relates the real storage area inside the pool to the virtual logical volume in units of a first real storage area that comprises a prescribed first size, and selects a second real storage area that has a prescribed second size from the first real storage area related to the virtual logical volume and allocates same to the virtual logical volume in accordance with a write request from the host computer, wherein   the first size is set to an integral multiple of the second size, and   control information related to a first real storage area concerned is stored in the first real storage area.   
     
     
         2 . A storage control apparatus according to  claim 1 , wherein
 the virtual logical volume is coupled to the host computer and to another storage control apparatus via a communication network, and   the host computer is configured as a mainframe,   the controller has: an allocation controller for allocating the first real storage area and the second real storage area to the virtual logical volume; a correspondence managing unit for managing a corresponding relationship between the virtual logical volume, the first real storage area, and the second real storage area; an access request processor for processing an access request from the host computer to the virtual logical volume based on the corresponding relationship managed by the correspondence managing unit; and a copy controller, which creates a copy-pair between the virtual logical volume and another logical volume inside the other storage control apparatus and copies data between the virtual logical volume and the other logical volume,   the first real storage area that is allocated to the virtual logical volume has a user area, which the host computer is able to access via the access request processor, and a control area for storing the control information to be used by the copy controller,   the allocation controller expands a volume size of the virtual logical volume in units of the first real storage area without suspending access to the virtual logical volume from the host computer,   the controller provides to the host computer only the user area of the first real storage area allocated to the virtual logical volume,   the controller, in a case where prescribed data inside the user area is accessed by the host computer, specifies the control information corresponding to the prescribed data based on an access-destination address of the host computer and updates the specified control information, and   the copy controller copies difference data generated in the user area by transferring this difference data to the other logical volume based on the control information stored in the control area.   
     
     
         3 . A storage control apparatus according to  claim 1 , wherein
 the control information is stored either at the start or the end of the first real storage area,   another area of the first real storage area besides the area in which the control information is stored is the user area that is able to be used by the host computer, and   the controller provides the host computer with only the user area, enabling access thereto.   
     
     
         4 . A storage control apparatus according to  claim 3 , wherein the controller, in a case where prescribed data of the user area is accessed by the host computer, specifies a location of the control information corresponding to the prescribed data based on the access-destination address of the host computer. 
     
     
         5 . A storage control apparatus according to  claim 3 , wherein the virtual logical volume forms a copy-pair with the other logical volume, and the control information includes copy management information for managing the copy-pair. 
     
     
         6 . A storage control apparatus according to  claim 5 , wherein the copy management information includes information showing a type of the copy-pair. 
     
     
         7 . A storage control apparatus according to  claim 5 , wherein the copy management information includes:
 information for managing a difference between the storage content of the virtual logical volume and the storage content of the other logical volume;   internal copy information for showing that the other logical volume and the virtual logical volume are disposed in the same storage control apparatus; and   external copy information for showing that the other logical volume and the virtual logical volume are disposed in different storage control apparatuses.   
     
     
         8 . A storage control apparatus according to  claim 5 , wherein the control information includes a reserved bit prepared for future functional expansion. 
     
     
         9 . A storage control apparatus according to  claim 1 , wherein the virtual logical volume is configured from a real logical volume and the second real storage area that is allocated from the pool. 
     
     
         10 . A storage control apparatus according to  claim 1 , wherein the virtual logical volume is configured only from the second real storage area that is allocated from the pool. 
     
     
         11 . A storage control apparatus according to  claim 1 , wherein the real storage area inside the pool has a RAID configuration. 
     
     
         12 . A storage control apparatus according to  claim 1 , wherein the host computer is a mainframe. 
     
     
         13 . A method for controlling a virtual logical volume, which is a virtually created logical volume, the method comprising: in a case where a volume size of the virtual logical volume is expanded,
 allocating a real storage area, which is managed in a pool, to the virtual logical volume in units of a first real storage area that has a prescribed first size without suspending access from a host computer;   selecting a second real storage area that has a prescribed second size from the first real storage area allocated to the virtual logical volume and allocating same to the virtual logical volume in accordance with a write request from the host computer;   setting the first size to an integral multiple of the second size;   storing control information related to the first real storage area in this first real storage area; and   providing the host computer with an area, which excludes the control information of the first real storage area, as a user area.